Aluminium Router

[lessthanmore]

Dear All,

I would like to build my first CNC router, and as I finally decided what size it will be (based on the ballscrews and rails) I made a plan in SketchUp.
I intend to cut aluminium, wood and plastic with the machine. I don't know whether this could handle steel too, I guess not... would be nice though
I would like you to check it, and give me some feedback. Please tell me if there is anything I could improve before I build it. I haven't bought any extrusions nor aluminium plates, nor square tubes yet, so the design may change if necessary.

About the components (all Chinese stuff):

• steppers: 4 pieces of Nema 23 425 oz in
• spindle: 2.2kw water cooled
• ballscrews: SFU1605
• linear rails: SBR20

The X axis (so the longest one) has 2 ballscrews, which are 1180mm long each, the linear rails are 1300mm so the travel length with this design is a little over 1000mm (~1018mm in SketchUp). On the linears I have 2 SBR20LUU bearings, so they are the longer versions, between the 2 bearings there is 82mm, so the total length of the gantry side is 274 mm (96mm + 96mm + 82mm). The rails and the ballscrews are attached to a 40x80mm aluminium extrusion.
The Y axis has a 1050mm ballscrew with 1000mm rails 212mm apart from each other with normal SBR20UU bearings. The distance between the bearings is 60mm, so the overall width of the Z axis plate is 160mm. This gives me about 800mm travel length (~828mm).
The Z axis has a 250mm ballscrew with 300mm rails, they are 115mm apart from each other, also with SBR20UU bearings. The distance between the bearings here is also 60mm, with that I get a 130mm travel length.

I designed the gantry plates from 20mm aluminium plates, although I haven't done any weight calculations yet, so I'm not sure if I should replace the back plate of the gantry with 2 40x80 extrusions, or it doesn't really matter. This seems more rigid to me
The base plate is also 20mm thick aluminium (I would like to drill a lot of holes on it and thread them). The OSB plate is just for visualizing the cut area.
The table is made from 40x40mm 3mm thick steel square tubes, welded together.
The shaft couplings are the flexible aluminium couplings, I hope they are strong enough.
I designed some covering on the X axis ballscrews, and I just made them see-through to show what there is (same with the Z axis plates).
Distance between the top of the Z axis stepper and the base plate is 635 mm.

I plan on installing proximity sensors as limit switches, and some cooling system too, not sure what though. Dust shoe for wood might come later.

I don't have any machining experience yet (I am just "YouTube-educated") so when I do something wrong, that's just because I'm a newcomer.
Any comments, questions and suggestions are welcome

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[fretman_2]

Gantry plates 2mm aluminum?? Is that a typo? I would suggest you make your gantry plates out of something much, much thicker and then make your gantry beam much beefier too. Gantry side plates and gantry beam can't be too stiff. When I was designing my machine, I was told to not worry about weight...that weight was your friend!

Good luck with your build!

Dear All,

I would like to build my first CNC router, and as I finally decided what size it will be (based on the ballscrews and rails) I made a plan in SketchUp.
I intend to cut aluminium, wood and plastic with the machine. I don't know whether this could handle steel too, I guess not... would be nice though
I would like you to check it, and give me some feedback. Please tell me if there is anything I could improve before I build it. I haven't bought any extrusions nor aluminium plates, nor square tubes yet, so the design may change if necessary.

About the components (all Chinese stuff):

• steppers: 4 pieces of Nema 23 425 oz in
• spindle: 2.2kw water cooled
• ballscrews: SFU1605
• linear rails: SBR20

The X axis (so the longest one) has 2 ballscrews, which are 1180mm long each, the linear rails are 1300mm so the travel length with this design is a little over 1000mm (~1018mm in SketchUp). On the linears I have 2 SBR20LUU bearings, so they are the longer versions, between the 2 bearings there is 82mm, so the total length of the gantry side is 274 mm (96mm + 96mm + 82mm). The rails and the ballscrews are attached to a 40x80mm aluminium extrusion.
The Y axis has a 1050mm ballscrew with 1000mm rails 212mm apart from each other with normal SBR20UU bearings. The distance between the bearings is 60mm, so the overall width of the Z axis plate is 160mm. This gives me about 800mm travel length (~828mm).
The Z axis has a 250mm ballscrew with 300mm rails, they are 115mm apart from each other, also with SBR20UU bearings. The distance between the bearings here is also 60mm, with that I get a 130mm travel length.

I designed the gantry plates from 2mm aluminium plates, although I haven't done any weight calculations yet, so I'm not sure if I should replace the back plate of the gantry with 2 40x80 extrusions, or it doesn't really matter. This seems more rigid to me
The base plate is also 2mm thick aluminium (I would like to drill a lot of holes on it and thread them). The OSB plate is just for visualizing the cut area.
The table is made from 40x40mm 3mm thick steel square tubes, welded together.
The shaft couplings are the flexible aluminium couplings, I hope they are strong enough.
I designed some covering on the X axis ballscrews, and I just made them see-through to show what there is (same with the Z axis plates).
Distance between the top of the Z axis stepper and the base plate is 635 mm.

I plan on installing proximity sensors as limit switches, and some cooling system too, not sure what though. Dust shoe for wood might come later.

I don't have any machining experience yet (I am just "YouTube-educated") so when I do something wrong, that's just because I'm a newcomer.
Any comments, questions and suggestions are welcome

[lessthanmore]

Ooops, yes that is a typo that is 20mm (2cm), I edit it thanks!

So I did some calculations:
- gantry weight: 54 kg (this is the total weight that sits on the X axis linear bearings)
- base plate weight: 64 kg
- table weight: 65 kg

All in all the machine would weight about 220 kg

[fretman_2]

LOL...

Ooops, yes that is a typo that is 20mm (2cm), I edit it thanks!

So I did some calculations:
- gantry weight: 54 kg (this is the total weight that sits on the X axis linear bearings)
- base plate weight: 64 kg
- table weight: 65 kg

All in all the machine would weight about 220 kg

[lessthanmore]

I made some changes:
- the X axis ballscrews are now on the inside rather than the outside (so they no longer stick out of the machine).

- the base plate and the gantry are narrower. There is only 42 mm on each side between the cover of the ballscrew and the edge of the cut area (it was 90mm before). This makes the base plate 6 kg and the gantry about 1,6 kg lighter.

- the table is now 40mm wider.

- unfortunately the Y axis ballscrew is 50 mm longer than the Y axis linear rails, so the end sticks out. It doesn't look awful, but I'm not quite sure if I should avoid such design, as I assume it would be more reliable if both ends of the ballscrew would be mounted on the rigid back plate of the gantry. Of course I could cut the gantry plate to have a protruding part but that is more complicated.

- the Z axis is now as short as possible. This makes it about 41mm lower, the stepper doesn't stick out as much anymore.

[lessthanmore]

I have a question, should I avoid to join the gantry to the ballscrew in such way? So not directly connected to the housing, but with a plate perpendicular to the gantry side wall (the purple part)? Would it be strong enough with the 2 screws on each side? I made this change so I could put the bearing blocks (almost) directly on the aluminium extrusion. If I would go with the original idea, the bearing blocks should be about 22mm away, but with this design they could be mounted with 2mm separators to the extrusion. (the shaft of the stepper is about 2mm off center to the ballscrew, that's why the 2mm is needed)

[wizard]

I made some changes:
- the X axis ballscrews are now on the inside rather than the outside (so they no longer stick out of the machine).

- the base plate and the gantry are narrower. There is only 42 mm on each side between the cover of the ballscrew and the edge of the cut area (it was 90mm before). This makes the base plate 6 kg and the gantry about 1,6 kg lighter.

You seem to be focused on lightness when your focus should be rigidity. Especially if you want success in the machining of metals. So from that perspective I'd seriously consider a box beam of some sort for the gantry and stiffer support plates.

- the table is now 40mm wider.

- unfortunately the Y axis ballscrew is 50 mm longer than the Y axis linear rails, so the end sticks out. It doesn't look awful, but I'm not quite sure if I should avoid such design, as I assume it would be more reliable if both ends of the ballscrew would be mounted on the rigid back plate of the gantry. Of course I could cut the gantry plate to have a protruding part but that is more complicated.

If you can get the parts properly aligned the specific position of the parts doesn't matter. That is as long as you don't have huge over hung loads. In any event if the screw is too long why not cut it to fit?

- the Z axis is now as short as possible. This makes it about 41mm lower, the stepper doesn't stick out as much anymore.

Make sure you have enough Z travel to clear all the tooling you are likely to use. Note this is different than the clearance under the gantry.

[lessthanmore]

Thanks for the reply.
I actually didn't do these modifications to make the machine lighter, but to make it more "user friendly". Imagine how many times would I bump into such protruding parts like the ballscrews seen on the first design, I think with the whole setup being equally wide - at least at table level - it is more easy to move around it. I believe that more weight = more rigid, but it is still over 50kg (more than 110 lbs) so honestly I just hope those steppers will be able to move it

To make it stiffer I added corner plates to each corner where the gantry parts meet.

Oh and I ended up using the previously mentioned design with the Y ballscrew (I am confused whether the gantry axis is the X or Y, as I see both in use) as I changed the ballscrew nut housing, and it turned out they line up perfectly with the linear guides... That's why I should check the dimensions of all parts being downloaded from the 3D Warehouse even though they look like the part I own, there might be a couple mm difference... So now both bearing blocks sit on the same plate, and with that it seems to be the simplest solution. I can't shorten the ballscrew as I don't have a lathe nor the skills to turn it

I didn't mean by saying the Z axis is now as short as possible that the travel is shortened, but the overall height of the assembly is optimized but the travel remained the same, it is still about 130mm. The distance between the tip of the empty spindle and the table top (with 10mm spoilboard attached) is 150mm, but that is without any bit. I plan to cut mostly planes so I am not worried about not being able to cut higher objects. But of course if I need more room, I can just slide the spindle up in its mount, this way I can get an extra 50mm. I tried to keep the gantry low, that's how it remains rigid. Oh and since the whole setup is based on two aluminium extrusions, it is quite easy to make it higher in case I need it just have to throw some extrusions under the existing ones.